function sysCall_init() 
    left_front_handle= sim.getObjectHandle('left_joint')
    left_back_handle= sim.getObjectHandle('left_joint')
    right_back_handle= sim.getObjectHandle('right_joint')
    right_front_handle= sim.getObjectHandle('right_joint')
    MaxVel=2
    leftvelocity=0
    rightvelocity=0
    dVel=100;
    --sim.setJointTargetVelocity(left_front_handle,leftvelocity)
    sim.setJointTargetVelocity(left_back_handle,leftvelocity)
    sim.setJointTargetVelocity(right_back_handle,rightvelocity)
    --sim.setJointTargetVelocity(right_front_handle,rightvelocity)
end

function sysCall_actuation() 
    message,auxiliaryData=sim.getSimulatorMessage()
    while message~=-1 do
        if (message==sim.message_keypress) then
            if (auxiliaryData[1]==32) then
                -- right key
                leftvelocity=0
                rightvelocity=0
                sim.setJointForce(left_front_handle, 0)
                sim.setJointForce(left_back_handle, 0)
                sim.setJointForce(right_back_handle, 0)
                sim.setJointForce(right_front_handle, 0)
                break
            else
                --sim.setJointForce(left_front_handle, 10000)
                sim.setJointForce(left_back_handle, 10000)
                sim.setJointForce(right_back_handle, 10000)
                --sim.setJointForce(right_front_handle, 10000)
            end
            if (auxiliaryData[1]==119) then
                -- w key
                leftvelocity=(leftvelocity+rightvelocity)/2
                rightvelocity=leftvelocity
                leftvelocity=leftvelocity+dVel
                rightvelocity=rightvelocity+dVel
            end
            if (auxiliaryData[1]==115) then
                -- s key
                leftvelocity=(leftvelocity+rightvelocity)/2
                rightvelocity=leftvelocity
                leftvelocity=leftvelocity-dVel
                rightvelocity=rightvelocity-dVel
            end
            if (auxiliaryData[1]==97) then
                -- a key
                leftvelocity=leftvelocity-dVel
                rightvelocity=rightvelocity+dVel
            end
            if (auxiliaryData[1]==100) then
                -- d key
                leftvelocity=leftvelocity+dVel
                rightvelocity=rightvelocity-dVel
            end
        end
        message,auxiliaryData=sim.getSimulatorMessage()
    end
    
    if leftvelocity>MaxVel then
        leftvelocity=MaxVel
    end
    if leftvelocity<-MaxVel then
        leftvelocity=-MaxVel
    end
    
    if rightvelocity>MaxVel then
                rightvelocity=MaxVel
    end
    if rightvelocity<-MaxVel then
                rightvelocity=-MaxVel
    end
    
    --sim.setJointTargetVelocity(left_front_handle,leftvelocity)
    sim.setJointTargetVelocity(left_back_handle,leftvelocity)
    sim.setJointTargetVelocity(right_back_handle,rightvelocity)
    --sim.setJointTargetVelocity(right_front_handle,rightvelocity)
    
end